crypto.c

   1 /*
   2  * Copyright (c) 2008 The DragonFly Project.  All rights reserved.
   3  *
   4  * This code is derived from software contributed to The DragonFly Project
   5  * by Matthias Schmidt <matthias@dragonflybsd.org>, University of Marburg,
   6  * Germany.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  *
  12  * 1. Redistributions of source code must retain the above copyright
  13  *    notice, this list of conditions and the following disclaimer.
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice, this list of conditions and the following disclaimer in
  16  *    the documentation and/or other materials provided with the
  17  *    distribution.
  18  * 3. Neither the name of The DragonFly Project nor the names of its
  19  *    contributors may be used to endorse or promote products derived
  20  *    from this software without specific, prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  23  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  24  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  25  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  26  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  27  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  28  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  29  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  30  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  31  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  32  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  34  */
  35
  36 #include <openssl/x509.h>
  37 #include <openssl/md5.h>
  38 #include <openssl/ssl.h>
  39 #include <openssl/err.h>
  40 #include <openssl/pem.h>
  41 #include <openssl/rand.h>
  42
  43 #include <syslog.h>
  44
  45 #include "dma.h"
  46
  47 static int
  48 init_cert_file(SSL_CTX *ctx, const char *path)
  49 {
  50         int error;
  51
  52         /* Load certificate into ctx */
  53         error = SSL_CTX_use_certificate_chain_file(ctx, path);
  54         if (error < 1) {
  55                 syslog(LOG_ERR, "SSL: Cannot load certificate `%s': %s", path, ssl_errstr());
  56                 return (-1);
  57         }
  58
  59         /* Add private key to ctx */
  60         error = SSL_CTX_use_PrivateKey_file(ctx, path, SSL_FILETYPE_PEM);
  61         if (error < 1) {
  62                 syslog(LOG_ERR, "SSL: Cannot load private key `%s': %s", path, ssl_errstr());
  63                 return (-1);
  64         }
  65
  66         /*
  67          * Check the consistency of a private key with the corresponding
  68          * certificate
  69          */
  70         error = SSL_CTX_check_private_key(ctx);
  71         if (error < 1) {
  72                 syslog(LOG_ERR, "SSL: Cannot check private key: %s", ssl_errstr());
  73                 return (-1);
  74         }
  75
  76         return (0);
  77 }
  78
  79 int
  80 smtp_init_crypto(int fd, int feature, struct smtp_features* features)
  81 {
  82         SSL_CTX *ctx = NULL;
  83 #if (OPENSSL_VERSION_NUMBER >= 0x00909000L)
  84         const SSL_METHOD *meth = NULL;
  85 #else
  86         SSL_METHOD *meth = NULL;
  87 #endif
  88         X509 *cert;
  89         int error;
  90
  91         /* XXX clean up on error/close */
  92         /* Init SSL library */
  93         SSL_library_init();
  94         SSL_load_error_strings();
  95
  96         // Allow any possible version
  97 #if (OPENSSL_VERSION_NUMBER >= 0x10100000L)
  98         meth = TLS_client_method();
  99 #else
 100         meth = SSLv23_client_method();
 101 #endif
 102
 103         ctx = SSL_CTX_new(meth);
 104         if (ctx == NULL) {
 105                 syslog(LOG_WARNING, "remote delivery deferred: SSL init failed: %s", ssl_errstr());
 106                 return (1);
 107         }
 108
 109         /* User supplied a certificate */
 110         if (config.certfile != NULL) {
 111                 error = init_cert_file(ctx, config.certfile);
 112                 if (error) {
 113                         syslog(LOG_WARNING, "remote delivery deferred");
 114                         return (1);
 115                 }
 116         }
 117
 118         /*
 119          * If the user wants STARTTLS, we have to send EHLO here
 120          */
 121         if (((feature & SECURETRANS) != 0) &&
 122              (feature & STARTTLS) != 0) {
 123                 /* TLS init phase, disable SSL_write */
 124                 config.features |= NOSSL;
 125
 126                 if (perform_server_greeting(fd, features) == 0) {
 127                         send_remote_command(fd, "STARTTLS");
 128                         if (read_remote(fd, 0, NULL) != 2) {
 129                                 if ((feature & TLS_OPP) == 0) {
 130                                         syslog(LOG_ERR, "remote delivery deferred: STARTTLS not available: %s", neterr);
 131                                         return (1);
 132                                 } else {
 133                                         syslog(LOG_INFO, "in opportunistic TLS mode, STARTTLS not available: %s", neterr);
 134                                         return (0);
 135                                 }
 136                         }
 137                 }
 138
 139                 /* End of TLS init phase, enable SSL_write/read */
 140                 config.features &= ~NOSSL;
 141         }
 142
 143         config.ssl = SSL_new(ctx);
 144         if (config.ssl == NULL) {
 145                 syslog(LOG_NOTICE, "remote delivery deferred: SSL struct creation failed: %s",
 146                        ssl_errstr());
 147                 return (1);
 148         }
 149
 150         /* Set ssl to work in client mode */
 151         SSL_set_connect_state(config.ssl);
 152
 153         /* Set fd for SSL in/output */
 154         error = SSL_set_fd(config.ssl, fd);
 155         if (error == 0) {
 156                 syslog(LOG_NOTICE, "remote delivery deferred: SSL set fd failed: %s",
 157                        ssl_errstr());
 158                 return (1);
 159         }
 160
 161         /* Open SSL connection */
 162         error = SSL_connect(config.ssl);
 163         if (error < 0) {
 164                 syslog(LOG_ERR, "remote delivery deferred: SSL handshake failed fatally: %s",
 165                        ssl_errstr());
 166                 return (1);
 167         }
 168
 169         /* Get peer certificate */
 170         cert = SSL_get_peer_certificate(config.ssl);
 171         if (cert == NULL) {
 172                 syslog(LOG_WARNING, "remote delivery deferred: Peer did not provide certificate: %s",
 173                        ssl_errstr());
 174         }
 175         X509_free(cert);
 176
 177         return (0);
 178 }
 179
 180 /*
 181  * hmac_md5() taken out of RFC 2104.  This RFC was written by H. Krawczyk,
 182  * M. Bellare and R. Canetti.
 183  *
 184  * text      pointer to data stream
 185  * text_len  length of data stream
 186  * key       pointer to authentication key
 187  * key_len   length of authentication key
 188  * digest    caller digest to be filled int
 189  */
 190 void
 191 hmac_md5(unsigned char *text, int text_len, unsigned char *key, int key_len,
 192     unsigned char* digest)
 193 {
 194         MD5_CTX context;
 195         unsigned char k_ipad[65];    /* inner padding -
 196                                       * key XORd with ipad
 197                                       */
 198         unsigned char k_opad[65];    /* outer padding -
 199                                       * key XORd with opad
 200                                       */
 201         unsigned char tk[16];
 202         int i;
 203         /* if key is longer than 64 bytes reset it to key=MD5(key) */
 204         if (key_len > 64) {
 205
 206                 MD5_CTX      tctx;
 207
 208                 MD5_Init(&tctx);
 209                 MD5_Update(&tctx, key, key_len);
 210                 MD5_Final(tk, &tctx);
 211
 212                 key = tk;
 213                 key_len = 16;
 214         }
 215
 216         /*
 217          * the HMAC_MD5 transform looks like:
 218          *
 219          * MD5(K XOR opad, MD5(K XOR ipad, text))
 220          *
 221          * where K is an n byte key
 222          * ipad is the byte 0x36 repeated 64 times
 223          *
 224          * opad is the byte 0x5c repeated 64 times
 225          * and text is the data being protected
 226          */
 227
 228         /* start out by storing key in pads */
 229         bzero( k_ipad, sizeof k_ipad);
 230         bzero( k_opad, sizeof k_opad);
 231         bcopy( key, k_ipad, key_len);
 232         bcopy( key, k_opad, key_len);
 233
 234         /* XOR key with ipad and opad values */
 235         for (i=0; i<64; i++) {
 236                 k_ipad[i] ^= 0x36;
 237                 k_opad[i] ^= 0x5c;
 238         }
 239         /*
 240          * perform inner MD5
 241          */
 242         MD5_Init(&context);                   /* init context for 1st
 243                                               * pass */
 244         MD5_Update(&context, k_ipad, 64);     /* start with inner pad */
 245         MD5_Update(&context, text, text_len); /* then text of datagram */
 246         MD5_Final(digest, &context);          /* finish up 1st pass */
 247         /*
 248          * perform outer MD5
 249          */
 250         MD5_Init(&context);                   /* init context for 2nd
 251                                               * pass */
 252         MD5_Update(&context, k_opad, 64);     /* start with outer pad */
 253         MD5_Update(&context, digest, 16);     /* then results of 1st
 254                                               * hash */
 255         MD5_Final(digest, &context);          /* finish up 2nd pass */
 256 }
 257
 258 /*
 259  * CRAM-MD5 authentication
 260  */
 261 int
 262 smtp_auth_md5(int fd, char *login, char *password)
 263 {
 264         unsigned char digest[BUF_SIZE];
 265         char buffer[BUF_SIZE], ascii_digest[33];
 266         char *temp;
 267         int len, i;
 268         static char hextab[] = "0123456789abcdef";
 269
 270         temp = calloc(BUF_SIZE, 1);
 271         memset(buffer, 0, sizeof(buffer));
 272         memset(digest, 0, sizeof(digest));
 273         memset(ascii_digest, 0, sizeof(ascii_digest));
 274
 275         /* Send AUTH command according to RFC 2554 */
 276         send_remote_command(fd, "AUTH CRAM-MD5");
 277         if (read_remote(fd, sizeof(buffer), buffer) != 3) {
 278                 syslog(LOG_DEBUG, "smarthost authentication:"
 279                        " AUTH cram-md5 not available: %s", neterr);
 280                 /* if cram-md5 is not available */
 281                 free(temp);
 282                 return (-1);
 283         }
 284
 285         /* skip 3 char status + 1 char space */
 286         base64_decode(buffer + 4, temp);
 287         hmac_md5((unsigned char *)temp, strlen(temp),
 288                  (unsigned char *)password, strlen(password), digest);
 289         free(temp);
 290
 291         ascii_digest[32] = 0;
 292         for (i = 0; i < 16; i++) {
 293                 ascii_digest[2*i] = hextab[digest[i] >> 4];
 294                 ascii_digest[2*i+1] = hextab[digest[i] & 15];
 295         }
 296
 297         /* prepare answer */
 298         snprintf(buffer, BUF_SIZE, "%s %s", login, ascii_digest);
 299
 300         /* encode answer */
 301         len = base64_encode(buffer, strlen(buffer), &temp);
 302         if (len < 0) {
 303                 syslog(LOG_ERR, "can not encode auth reply: %m");
 304                 return (-1);
 305         }
 306
 307         /* send answer */
 308         send_remote_command(fd, "%s", temp);
 309         free(temp);
 310         if (read_remote(fd, 0, NULL) != 2) {
 311                 syslog(LOG_WARNING, "remote delivery deferred:"
 312                                 " AUTH cram-md5 failed: %s", neterr);
 313                 return (-2);
 314         }
 315
 316         return (0);
 317 }